title: Mass spectrometry-based identification of the tumor antigen UN1 as the transmembrane CD43 sialoglycoprotein.
abstract: The UN1 monoclonal antibody recognized the UN1 antigen as a heavily sialylated and O-glycosylated protein with the apparent molecular weight of 100-120 kDa; this antigen was peculiarly expressed in fetal tissues and several cancer tissues, including leukemic T cells, breast, and colon carcinomas. However, the lack of primary structure information has limited further investigation on the role of the UN1 antigen in neoplastic transformation. In this study, we have identified the UN1 antigen as CD43, a transmembrane sialoglycoprotein involved in cell adhesion, differentiation, and apoptosis. Indeed, mass spectrometry detected two tryptic peptides of the membrane-purified UN1 antigen that matched the amino acidic sequence of the CD43 intracellular domain. Immunological cross-reactivity, migration pattern in mono- and bi-dimensional electrophoresis, and CD43 gene-dependent expression proved the CD43 identity of the UN1 antigen. Moreover, the monosaccharide GalNAc-O-linked to the CD43 peptide core was identified as an essential component of the UN1 epitope by glycosidase digestion of specific glycan branches. UN1-type CD43 glycoforms were detected in colon, sigmoid colon, and breast carcinomas, whereas undetected in normal tissues from the same patients, confirming the cancer-association of the UN1 epitope. Our results highlight UN1 monoclonal antibody as a suitable tool for cancer immunophenotyping and analysis of CD43 glycosylation in tumorigenesis.
authors.affiliation: Department of Experimental and Clinical Medicine, University of Catanzaro Magna Graecia, 88100 Catanzaro, Italy.
authors.forename: Annamaria
authors.initials: A
authors.lastname: de Laurentiis
authors.forename: Marco
authors.initials: M
authors.lastname: Gaspari
authors.forename: Camillo
authors.initials: C
authors.lastname: Palmieri
authors.forename: Cristina
authors.initials: C
authors.lastname: Falcone
authors.forename: Enrico
authors.initials: E
authors.lastname: Iaccino
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Fiume
authors.forename: Ornella
authors.initials: O
authors.lastname: Massa
authors.forename: Mariorosario
authors.initials: M
authors.lastname: Masullo
authors.forename: Franca Maria
authors.initials: FM
authors.lastname: Tuccillo
authors.forename: Laura
authors.initials: L
authors.lastname: Roveda
authors.forename: Ubaldo
authors.initials: U
authors.lastname: Prati
authors.forename: Olga
authors.initials: O
authors.lastname: Fierro
authors.forename: Immacolata
authors.initials: I
authors.lastname: Cozzolino
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Troncone
authors.forename: Pierfrancesco
authors.initials: P
authors.lastname: Tassone
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Scala
authors.forename: Ileana
authors.initials: I
authors.lastname: Quinto
mesh_terms: D000116:Acetylgalactosamine / Q000276:immunology; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology; D015180:Electrophoresis, Gel, Two-Dimensional; D000939:Epitopes; D005260:Female; D006031:Glycosylation; D006801:Humans; D051917:Leukosialin / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D053719:Tandem Mass Spectrometry
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000939:Epitopes; D051917:Leukosialin; C465014:SPN protein, human; D000116:Acetylgalactosamine